The invention concerns a linear rolling bearing comprising a shaft acting as a guide and having a profiled or round, particularly circular cross-section, an outer peripheral surface of the shaft forming raceways extending in longitudinal direction for rolling elements, for example, balls, cylindrical rollers or convex rollers, the linear rolling bearing further comprising a cup surrounding the shaft and the rolling elements, said cup comprising on an inner surface opposing raceways for the rolling elements while being arranged in a reception or a bore of a connecting structure.
The range of use of such linear rolling bearings includes linear guides that have a limited or an unlimited stroke length, flat or round or profiled raceways and in which the reception of the cup, or of a differently configured element that assumes the function of the cup, describes a circle or a plurality of circular paths. In typical uses, the ball cups can have straight or profiled raceways whose normal lines pass through the center, or the ball cups can have straight or profiled raceways whose normal lines form an angle with the enveloping circle about the center. Known uses include closed ring solid ball cups, torque cups as shown, for example, in the document DE 37 36 876 A1, pillar guides for tools and die sets that have a structure similar to pillar guides.
Closed ring ball cups can be made in a simple manner by inner and outer cylindrical grinding. This applies to commonly used dimensions. If cups of large dimensions are required, particularly with large axial lengths, inner cylindrical grinding becomes more difficult and expensive with increasing length. Due to their profiled inner contour, it is only with difficulty that torque cups can be manufactured. They have to be machined with small profiled tools and this can be time-consuming and cost-intensive and results in minimum material removal, high tool wear rates and the concomitant large scatter of tolerances that manifest themselves in profile errors, poor surface quality and inadequate parallelism of the raceways to the longitudinal axis.
It is an object of the invention to provide a linear rolling bearing that can be made economically to close tolerances and possesses a high degree of raceway parallelism and a good profile compliance.
This and other objects and advantages will become obvious from the following detailed description.
The invention achieves the above objects by the fact that the cup of the bearing has a divided configuration in longitudinal direction and is composed of a plurality of segments that comprise the opposing raceways and further comprise support surfaces extending parallel to the opposing raceways, through which support surfaces, the segments are supported on one another in peripheral direction of the cup. In this way, bearings hitherto configured with closed rings or with other closed contours, can be replaced with cups divided longitudinally into segments which may be joined or not joined to one another. The segments can comprise flat, round or otherwise profiled raceways. The longitudinal division permits inner machining with tools that are much larger than the inner diameter of a cup. By this, a more economic fabrication, closer tolerances, improved profile compliance and high raceway parallelism are achieved. The longitudinal division makes it possible to use simple guide elements that are mounted on or positioned relative to the segment in question, and the segments can support one another.
A cup having a closed cross-sectional contour, preferably an annular contour, is cut up in longitudinal direction into at least two parts or segments. These comprise one or more raceways on their inner surface and support one another through their end contours. With modern fabrication methods, raceways and support contours can be made with a profiled grinding wheel or with an appropriate tool, for example, a disk milling cutter, the tool profile comprising regions for the machining of raceways and regions for the machining of support surfaces.
The segments are inserted into a round or profiled but closed reception, for example, a bore in a housing, so that they are subjected to an annular pressure that is exerted by the housing. In this way, the radial position of the segments is uniquely defined. In the presence of forces acting towards the center, the segments can be supported through flat stop surfaces.
If transverse forces act on the segments, a tilting takes place about the highest point of the segment back. In this case, one of the stop surfaces has the tendency to move towards the center of the guide, while the other tends to move away from there. By an appropriate profiling of the stop surfaces, the segments can be supported on one another so that they act like a closed ring. Due to the higher precision of the raceways, a more rigid contact is obtained compared to a closed ring so that with an appropriate configuration of the stop surfaces, the drawback that joints exist has only a negligible effect, and an arrangement is obtained that is more rigid on the whole.
The segments can be fixed to one another in longitudinal direction by positively engaging elements, by rings e.g. securing rings, by welded joints or by end caps. In the reception, they can be fixed individually or as a complete unit by usual methods, for example, by securing rings, pins or screws.
Examples of embodiment of the invention will be described more closely below with reference to the appended drawings.